1. Field of Invention
The invention relates to a sheet-supply device that separates and feeds sheets, one by one, from a stack of sheets held in an inclined position by a hopper portion, and more particularly, to a sheet-supply device that prevents two or more sheets from being fed at one time during a sheet feed operation.
2. Description of Related Art
Commonly, various recording apparatuses, such as printers and facsimile machines, include a sheet-supply device that separates and feeds sheets, one by one, from a stack of sheets held by a hopper portion. Currently, two types of sheet-supply device are practical in use. One type of the sheet-supply device holds a plurality of sheets in a horizontal position, and another type of the sheet-supply device holds a plurality of sheets in an inclined position. Recently, the latter type of the sheet-supply device has been most commonly adopted to save installation space. However, because lower edges of the sheets in the inclined position are received by a lower edge receiving portion provided in a substantially horizontal position, the lower edges of the sheets are likely to slide over the lower edge receiving portion. In addition, there is a high possibility that two or more sheets are to be fed at one time (a multi-feed problem likely occurs) in the inclined-type sheet-supply device.
There have been proposed various multi-feed prevention techniques in the inclined-type sheet-supply devices. For example, U.S. Patent Application Publication No. US 2002/0011702 A1 discloses a paper feeder that includes a paper feeding roller, which is provided downstream of a hopper in a paper feed direction, and a rotatable paper returner, which is provided downstream in the paper feed direction, and has a separation pad. The paper returner stands up almost vertically for blocking accidental entry of paper into a paper transporting passage when paper is set. When the paper feeding roller rotates as paper feed starts, the paper returner is gradually inclined toward a fall-down position.
When the paper returner reaches the fall-down position and the hopper is moved up to a topmost position, a top sheet is pressed by the paper feeding roller and thus conveyed along the paper guide by the paper feeding roller. Then, the hopper moves down before a leading end of the fed paper arrives at transport rollers, and then the paper returner is rotated to a stand-up position. That is, the position of the paper returner is changed to the stand-up position while conveying the paper, resulting in preventing a multi-feed problem.
As described above, in the paper feeder disclosed in U.S. Patent Application Publication No. US 2002/0011702 A1, the paper returner is gradually rotated from the stand-up position to the fall-down position when paper feed starts, and the paper returner is gradually rotated from the fall-down position to the stand-up position as the leading end of the paper arrives at the transport rollers. However, while paper is being fed, that is, the paper returner is maintained at the fall-down position, the feeding of other sheets of paper and the top sheet in the paper feed direction is not regulated. Thus, there is a high possibility that two or more sheets of paper are fed at one time when paper feed is performed by the paper feeding roller.
Although it is conceivable that the multi-feed problem is prevented by changing the position of the paper returner to the stand-up position immediately after paper feed is started by the paper feeding roller, the paper returner cannot be rotated to the stand-up position because the paper returner is located under the paper feeding roller when the paper feed starts. In addition, when a plurality of sheets of paper are held by the hopper, no preventive measures are taken in order to prevent feeding two or more sheets of paper at one time even though there is a high possibility the multi-feed problem may occur.